Theory Of Operation; Repetition Rate Generator - HP 8082A Operating And Service Manual

4 - l
4 - 2 A basic black
shown in figure 4-1 and this should be referred to when
reading the follovving description. The pulse repetition
rate is generated either internally by the Rate Generator
or externally by an external input signal, depending on
the mode of operation. The square wave output of the
Rate Generator is input to the Transition Detector were
it is pulse shaped to produce a train of 2ns wide spikes.
These pulse spikes are then applied to the
Width Generators. Each of these generators is divided into
two parts for periods of l -5ns or
coming signal is routed into the appropriate part. The
Output of the Width Generator is level shifted and input
to the Slope Generator where the slope of the leading and
trailing pulse edges is made variable (variable transition
times).
4 - 3 If Double Pulse mode is selected, both the
delayed and undelayed waveforms are input to the Width
Generator. if External Width mode is selected, both the
Delay and Width Generators are by-passed and the output
of the Transition Detector is input to the level shifter.
The output of the Slope Gen.?rator
4 - 4
to one of two Buffer Amplifiers
sition time setting (l-5ns or > 5ns). Norma! 2nd comple-
outputs from the Buffer
to the dual channel Output Amplif
tude variation within ranges is added in the form of an
Vernier, which is common to both channels.
diagramof the 8082A is
is input
on the tran-
are then input
THEORY 4% OPERATION
The positive pulse DC Offset circuits are res-
4 - 5
ponsible for shifting the voltage level of both channels
from a negative level to a positive level, using the
POS switch, if positive output pulses are required (the
normal/complement relationship of the two channels is
also automatically reversed when this action is performed).
This means that either negative normal pulses or positive
normal pulses are available from one output connector.
4 - 6
After being set to the correct polarity, the
amplitude of both signals is set to the appropriate range
using an active Step Attenuator circuit.
4 - 7 Finally the External DC Offset circuit pro-
vides an offset voltage to shift the baseline of both out-
put signals together over the range -2V to
quired. This circuit can be switched off in which case
both signal baselines are at OV.
4 - 8
The function of the
4 - 9
is to provide a train of pulses, approximately 2ns wide,
for the delay generator or a 58% duty cycle waveform if
square wave is selected; also to provide a train of
duty cycle square wave pulses for the output trigger. A
block diagram of th? unit is given in Figure 4-2 and a
schematic diagram in Service Sheet 1.
rate generator